Light fixtures come in thousands of different shapes and sizes, colors and finishes. Plastic, metal, wood and glass are all common materials used in fixtures today. You can purchase fixtures at Big box stores, hardware stores and lighting specialty stores. The specialty stores generally carry a higher end price line of fixtures but can also order or have custom made fixtures done for you as well. Box stores do not usually provide that level of service.
If you need an inexpensive jelly jar fixture for outside your garage door, a $5.99 fixture is available everywhere. If you need an eight foot high chandelier for your main hallway or dining room for $8000 dollars, a specialty store would be more in line with your needs. Do not and I repeat, do not attempt to install or replace an eight foot chandler on your first try at fixture replacement. Start with an inexpensive jelly jar unit.
The very first thing you do is unpack the fixture and make sure everything is included. Fixture, screws, mounting plate, wire nuts, assembly instructions and so on. You will need a electrical current tester (voltmeter or test light), wire stripper tool, flat nosed pliers with side cutters and a screw driver.
The very next thing to do without exception is to turn off the power breaker to the power outlet at the main electrical panel. This is without exception. Your life could depend upon it. Do not get careless. Many people are injured each year thinking the power was turned off. Make sure it is without a doubt.. If you are afraid or not sure, call in a pro. Do not take chances. Ok now with the power breaker off, use your testing tool to assure the power is off at the outlet.
Carefully remove the wire nuts and touch a lead from your tester to each black and white wire. You should get no reading or light. If you do, you turned off the wrong breaker. Do it again. With no power, we can now safely remove the old fixture. Remove any screws or bolts holding the fixture, wire nuts, ground straps and carefully place the old fixture safely out of your way for disposal.
I find that many times the mounting bracket for the new fixture is the same as the old and does not need replacing. This saves a little work and time. First connect the bare copper fixture wire to the solid copper ground wire in the power cable in the gem box. This will ground the fixture and can provide a little support while you work.
Next connect the white fixture wire to the white power wire with the flat nosed pliers by twisting the last one inch of the wires together and then add one of the new wire nuts. Repeat this process with the black wire.The fixture is now wired. I then install a new bulb and turn on the switch. Having someone standing there, go to the main breaker and turn it on for a test.
If the fixture lights, you did the job well. If the breaker kicks off, you may have crossed the wires or have a bare wire touching the electrical box causing a short. Turn the breaker back off and check you work. Always work with the power off. Assuming the power test went well, return to the fixture and carefully tuck the wires into the gem box neatly being careful not to dislodge the wire nuts. Install the mounting screws to hold the fixture to the wall, add the required bulbs, chains, or other accessories and your done.
Turn the power back on. As you progress in replacing bigger and more complicated fixtures you may want to try installing a new fixture where one did not exist. In the national electrical code (NEC) which virtually all of the states recognize as the authority, a new fixture is an extension of the homes electrical system and requires an inspection by an underwriter. Many, many municipalities require a building or electrical permit for this work as well and also require you to submit to them a copy of the electrical certificate the underwriters will issue after inspection of the new work. Does this happen in real life? Not really but it is the code. Many fixtures are changed or added without permits or inspections and that is why so much care needs to be taken with this work.
People add on an outlet in a garage or basement and never give it a thought. A new fixture over the bathroom sink or even trading out a old style outlet for a newer type with a grounding hole technically are all changes to the homes electrical system. An incorrectly installed Ground Fault Interrupter outlet (GFI) can provide a false sense of security and protection and in fact offer none at all.
A faulty GFI can result in a death just to save $75 or so by an qualified electrician. I have found entire portions of a home rewired by the homeowner without regard to the number of outlets on a single breaker, lights wired to outlets, incorrect wire sizes, outlet placement and so on. All of these requirements are there for a reason.
You and your families safety depends on it. If you don't know the rules call in someone who does. Many localities today also require an electrician to have a license. If they do, ask to see it before he--she works on your home. Unauthorized alterations to a homes electrical system may cause you a great deal of grief with your insurance company in the case of a a fire or injury. In my area, a homeowner may perform his own work but is subject to the same rules and inspections as a licensed electrician.
If you decide you can handle adding a new fixture, the rules are pretty much the same for one light as ten lights. Check the amperage draw on the fixture, add it to the other items on that breaker and if it is less than the breakers capability (15 amps perhaps) then your good to go. We are installing an outside jelly jar at a side door in this example.
Find the closest power source that is fed from the panel. This may be an outlet but is seldom another light fixture. If you feed from an existing fixture, that fixture will have to be on for you to operate your new fixture and thats generally a no, no. If you locate a nearby outlet that is powered unless the breaker is off, check the inside of the box for the number of wires. If it is two wires or less, you have a good place to tie into the electrical system without overloading the electrical box..
With the breaker in the off position, carefully unscrew the existing outlet and pull it gently out of the box. The wires will come with it at the same time exposing the wire nuts. Run you new electrical wire from the existing box to the new box you installed for the light switch and the fixture by the door. The minimum size wire would be fourteen gage wire.
I use all twelve gage for extra safety. Your wire will have a black, a white and a solid copper wire inside the jacket. Pull the wire into and through the electrical boxes at both ends. Leave about one foot of wire sticking out of all boxes. If you are using plastic gem boxes, they will have a tab that holds the wire in place with no further work to hold the wire. If you are using metal gem boxes, you will find a clamp and screw inside the box that must be tightened to secure the power wire in place.
Tighten the screw well but not enough to crimp or cut the plastic jacket wrap on your power wire. If the new wire is in exposed stud walls, fasten the wire to the studs with the proper electrical staples. One staple should be within four to six inches of the boxes and the rest of the wire must be sufficiently stapled to secure the wire in place. Again, do not drive the staples so deep that you cut or crimp the wires jacket.
Unpack your jelly jar fixture and install it according to the instructions included with the fixture. These are simple fixtures with only two mounting screws to secure the fixture bracket to the gem box, three wire nuts to connect the black, white and copper ground wires and two final screws or nuts to affix the fixture to the mounting bracket.. Install the bulb and any covers or glass.
Now install your switch. Connect the two bare copper wires together with a wire nut and pack tightly into the back of the box. Connect the two white wires together with a wire nut and also pack them into the box. Now using the two black wires, strip back ¾ inch of wire wrap, curve the wire ends into a loop and fasten securely under the screws on the side of the switch. I like to wrap one strip of electricians black tape around my switches and outlets to cover the screws. When removing these later, it helps prevent an accidental shock from someone placing their fingers across the screws. Fasten the switch into the gem box with the screws provided.
Moving to the end of the wire where you are getting your power we will assume it is at an outlet for this example. Strip back the exterior plastic jacket on your cable as far into the box as you can reach exposing the three wires inside. Be careful not to damage the outside wrap on the black and white wires. The copper wire has no covering. Connect the solid copper wire to the other solid copper wires in the gem box or the green colored screw on the outlet if one is available.
This completes the ground wire. Connect the black and white wires to the outlet. Make sure white is connected to white and black is connected to black. Do not cross these wire colors or you will create a dead short in the system. One method on newer outlets is to strip back approximately ¾ of an inch of wire covering and stab the wire into the proper hole in the back of the outlet. You will see that the black and white wires are on opposing holes on each side.
If black is in the top hole on one side, the white is in the bottom hole on the other. This configuration will make both receptacles openings have power. A better method is to strip your wires and connect to the screws on the sides of the outlet. The screws are chrome or silver and brass colored. An easy reminder for yourself is black= brass or B to B. When you connect your wire for your outlet, just use the remaining two opposing holes and you will have full time power to your light switch. Replace the outlet back into it's original position in the box.
Turn your breaker back on at this point. If all your work was done correctly the breaker will stay on with no problem. If it kicks off, you have a short and you must recheck your work. Turn the breaker back on and check all the wire nuts and wires to assure none are crossed, touching each other or the metal boxes, etc. If the breaker stays on, try the light switch to assure the fixture lights properly. If the fixture works correctly, install your plate and outlet covers. Your jelly jar light is done.
All fixtures are basically the same with perhaps more mounting bolts or screws and many have dozens of parts to assemble but the wiring portion is the same. Once you have this basic wiring method well learned you can progress to three and four way switches and other more complicated wiring chores.